The Scythians: Who Were They?

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The Scythians: Who Were They? Mar 27, 2021 0:34:50 GMT

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Admixture modeling of IA steppe populations

Genetic ancestry modeling of the IA groups performed with qpWave and qpAdm confirmed that the steppe_MLBA groups adequately approximate the western Eurasian ancestry source in IA Scythians while the preceding steppe_EBA (e.g., Yamnaya and Afanasievo) do not (data file S4). As an eastern Eurasian proxy, we chose LBA herders from Khovsgol in northern Mongolia based on their geographic and temporal proximity. Other eastern proxies fail the model because of a lack or an excess of affinity toward the Ancient North Eurasian (ANE) lineage (25). However, this two-way admixture model of Khovsgol + steppe_MLBA does not fully explain the genetic compositions of the Scythian gene pools (data file S4). We find that the missing piece matches well with a small contribution from a source related to ancient populations living in the southern regions of the Caucasus/Iran or Turan [we use the term “Turan” for consistency with (7), only its geographical meaning, designating the southern part of Central Asia; Fig. 3A]. The proportions of this ancestry increase through time and space: a negligible amount in the most northeastern Aldy_Bel_700BCE group, ~6% in the early Tasmola_650BCE, ~12% in Pazyryk_Berel_50BCE, ~10% in Sargat_300BCE, ~13% in Saka_TianShan_600BCE, and ~20% in Saka_TianShan_400BCE (Fig. 3A), in line with f4-statistics (table S2). Sarmatians also require 15 to 20% Iranian ancestry while carrying substantially less Khovsgol and more steppe_MLBA-related ancestry than the eastern Scythian groups.

Fig. 3 Bar plots showing the ancestry proportions and SEs obtained from qpWave/qpAdm modelings.

(A) Fitting models for the main IA groups using LBA sources, the major genetic shift with the “new” East Asian influx (DevilsCave_N-like) observed in the Middle IA outliers and Korgantas. (B) Fitting models for the post-IA groups using IA groups as sources. A transparency factor is added to the models presenting poor fits (P < 0.05; only Konyr_Tobe_300CE). On the top is shown the color legend for the sources tested. (C) Summary of the admixture dates obtained with DATES for the main groups studied. The y axis is the temporal scale from BCE (negative) to CE (positive) dates. The x axis represents the results for the different target groups reported in the legends in each box using the two-way sources reported at the bottom of the three panels formed along the x axis (e.g., source1 + source2). The colored bars represent the date ranges of the culture, while the filled symbols show the admixture dates ± SEs obtained from DATES and converted into dates considering 29 years per generation starting from the median point of the culture’s age. The three set of sources reported correspond to the summary of the main admixture events described in the text from left to right: the LBA formation of the Scythian gene pools; the BMAC-related influx increasing through time in the Tian Shan Sakas; and the new eastern influx starting in the IA and continuing throughout the centuries. A number-based key (the white numbers from 1 to 6 inside the black circles) connects different tests and analyses shown in the figure with the corresponding arrow in Fig. 4.

For Sarmatians and later Tian Shan Sakas, only the groups from Turan (i.e., Turan_ChL, BMAC, and postBMAC) match as sources, while groups from Iran and Caucasus fail; we chose BMAC and postBMAC as the representative proxies (Fig. 3A and data file S4). The extra eastern Eurasian influx in the outliers (Tasmola_Birlik_640BCE, Korgantas_300BCE, and Pazyryk_Berel_50BCE_o) is not sourced from the same eastern proxies as the previous groups (i.e., Khovsgol); instead, it can only be modeled with an ancient northeast Asian (ANA) lineage, represented by the early Neolithic groups from the Devil’s Gate Cave site in the Russian Far East (DevilsCave_N) (Fig. 3A and data file S4).

Post-IA genetic turnovers in the Kazakh Steppe

We observe an intensification of the new eastern Eurasian influx described above among the individuals from the early 1st millennium CE (“Xianbei_Hun_Berel_300CE”) as well as the later 7th- to 11th-millennium CE individuals (“Karakaba_830CE” and “Kayalyk_950CE”). They are scattered along PC1 from the main IA Tasmola/Pazyryk cluster toward the ANA groups (Fig. 2C). The two individuals associated with Hun elite burials dated from the third century CE, one from the site of Kurayly in the Aktobe region in western Kazakhstan and the other from Budapest, Hungary (“Hun_elite_350CE”), cluster closely together along this cline (Fig. 2C and figs. S1 to S3).

The individuals from the ancient city of Otyrar Oasis in southern Kazakhstan show a quite distinct genetic profile. Three of five individuals (“Konyr_Tobe_300CE”) fall close to the published Kangju_250CE individuals from a similar time period and region (11), between Sarmatians and BMAC (Fig. 2C). KNT005 is shifted toward BMAC in PCA (Fig. 2C and fig. S1). Furthermore, KNT005 is the only one carrying a South Asian Y haplogroup, L1a2 (data file S1), and showing a South Asian genetic component in ADMIXTURE (Fig. 2D and fig. S2). KNT004 is shifted in PC1 toward East Asians (figs. S1 to S3). Admixture models including ~10% South Asian and ~50% eastern Eurasian influx adequately explain KNT005 and KNT004, respectively (data file S4). In contrast, the individuals from the site of Alai Nura (Alai_Nura_300CE) in the Tian Shan mountains (~200 km east from the Konyr Tobe site) still lay along the IA cline of the Tian Shan Saka, with four individuals falling closer to Konyr_Tobe_300CE and four closer to the Tasmola/Pazyryk cloud (Fig. 2C and figs. S1 to S3).

Dating ancient admixture

Admixture dating with the DATES program reveal an early formation of the main Scythian gene pools during 1000 to 1500 BCE (Fig. 3C and fig. S4). DATES is designed to model only the two-way admixture, so to account for the estimated three-way models obtained with qpWave and qpAdm, we independently tested the three pairwise comparisons (steppe_MLBA, BMAC, and Khovsgol). DATES was successful in fitting exponential decays for the two western + eastern Eurasian pairs, steppe_MLBA + Khovsgol, and BMAC + Khovsgol, while failing in the western + western Eurasian pair (steppe_MLBA + BMAC) (fig. S4 and table S3). For each target, steppe_MLBA + Khovsgol and BMAC + Khovsgol yielded nearly identical admixture date estimates (table S3). We believe that our estimates mostly reflect an average date between the genetically distinguishable eastern (Khovsgol) and western (steppe_MLBA + BMAC) ancestries, weighted by the relative contribution from the two western sources, rather than reflecting a true simultaneous three-way admixture. It is noteworthy that DATES found increasingly younger admixture dates in the Tian Shan Saka groups as the BMAC-related ancestry increases: from Saka_TianShan_600BCE to the Saka_TianShan_400BCE and especially in the later Alai_Nura_300CE as well as for Pazyryk_Berel_50BCE and Sargat_300BCE with respect to the date of Tasmola_650BCE (~1100 to 900 BCE with respect to ~1300 to 1400 BCE; Fig. 3C). A small-scale gene flow from a BMAC-related source continued over IA may explain both the increase in the BMAC-related ancestry proportion and increasingly younger admixture dates (Fig. 3A). Again, the inferred dates reflect an average over the IA admixture with a BMAC-related source and the LBA one with steppe_MLBA; therefore, they are likely shifted toward older time periods than the actual time of the IA gene flow.

Confirming the results from qpAdm, the admixed individuals from Tasmola_Birlik_640BCE and Korgantas_300BCE (“admixed_Eastern_out_IA”) show very recent admixture dates (Fig. 3C, fig. S4, and table S3). The later groups of Xianbei_Hun_Berel_300CE, Hun_elite_350CE, and Karakaba_830CE further corroborate this trend of recent dates of admixture, revealing that this new eastern influx likely started in the IA and continued at least during the first centuries of the first millennium CE (Fig. 3C, fig. S4, and table S3).

Present-day Kazakhs

PCA, ADMIXTURE, and CHROMOPAINTER/fineSTRUCTURE fine-scale haplotype-based analyses performed on present-day Kazakhs reveal a tight clustering and absence of detectable substructure among Kazakhs regardless of the geographic location or Zhuz affiliation (Fig. 2 and fig. S5). We still grouped the Kazakh individuals according to their Zhuz affiliations (which roughly reflects their geographic origin) and ran Globetrotter analyses following the pipeline in (26) as independent replicates to identify the different ancestry sources contributing to the gene pool of Kazakhs and date admixture events. Globetrotter analyses confirmed that the three groups have the same source composition and admixture dates and are a result of a complex mixture of different western, southern, and eastern Eurasian ancestries (table S4). The dates of admixture identified by Globetrotter highlight a narrow and recent time range for the formation of the present-day Kazakh gene pool, between 1341 and 1544 CE (table S5).

Last Edit: Mar 27, 2021 0:36:03 GMT by Admin

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The Scythians: Who Were They? Mar 27, 2021 3:55:40 GMT

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DISCUSSION

Our analysis of more than 100 ancient individuals from Central Asia shows that IA nomad populations of the Kazakh Steppe formed through extensive admixture, resulting from complex interactions between preceding MLBA populations from the steppe and the neighboring regions (Figs. 2A, 3, A and C, and 4A). Our findings shed new light onto the debate about the origins of the Scythian cultures. We do not find support for a western Pontic-Caspian steppe origin, which is, in fact, highly questioned by more recent historical/archeological work (1, 2). The Kazakh Steppe origin hypothesis finds instead a better correspondence with our results, but rather than finding support for one of the two extreme hypotheses, i.e., single origin with population diffusion versus multiple independent origins with only cultural transmission, we found evidence for at least two independent origins as well as population diffusion and admixture (Fig. 4B). In particular, the eastern groups are consistent with descending from a gene pool that formed as a result of a mixture between preceding local steppe_MLBA sources (which could be associated with different cultures such as Sintashta, Srubnaya, and Andronovo that are genetically homogeneous) and a specific eastern Eurasian source that was already present during the LBA in the neighboring northern Mongolia region (27). The genetic structure of the Early IA Tasmola culture of central and northern Kazakhstan is mostly composed of an equal mixture of these two ancestries, although smaller amounts of gene flow from an Iranian-related source are also required (Figs. 3A and 4A and data file S4). We found that overall BMAC-related populations from Turan provide the best fit to our models while Iranian-related sources further to the west, such as the BA groups from the northern Caucasus, fail (data file S4). These results corroborate the historical/archaeological hypotheses of a cultural connection between the southern civilizations and the northern steppe people (3). This BMAC influx continues in the later fourth- to first-century BCE-CE Scythian groups from the northeastern Pazyryk site of Berel and becomes increasingly higher and nonuniformly distributed in the southeastern Saka individuals from the Tian Shan mountains (Figs. 2, B and D, 3, A and C, and 4B; fig. S4; table S3; and data file S4).

Fig. 4 Summary maps describing the major genetic turnovers that occurred at the turn and throughout the first millennium BCE.

(A) Formation of a three-way LBA admixture cline from which (B) eastern Scythian and western Sarmatian gene pools arose and spread throughout the Steppe and (C) a new source of eastern Eurasian ancestry influx admixing with the Scythian gene pools started in the IA and becoming predominant and widespread at northern latitudes during the Xianbei-Hun period. On the very southern tips of the Steppe, a very different ancestry shift occurred, likely linked with the expansion of the Persian world. The arrows represent the demographic processes analyzed in the present study and are numbered from 1 to 6 to connect them to the main results shown in Fig. 3 from which these inferences have been drawn.

The two previously published individuals from the Aldy-Bel culture of the Arzhan 2 site in the Tuva region fall within the main eastern Scythian genetic cluster, confirming that it was present also in the same site where the earliest Scythian burials are found (Fig. 2A). These data, coupled with recent findings from the IA transition in Mongolia (28), seem to point to an origin in the Altai area of a main genetic substratum that formed all the eastern Scythians (Fig. 4B). The western Sarmatians from the southern Ural region also formed as a result of admixture between the same three ancestral sources as the eastern Scythians (Fig. 3A). Nevertheless, the eastern Eurasian ancestry is present only in a small amount in Sarmatians (Fig. 3A). In addition, their early admixture dates (Fig. 3C) and the absence of an admixture cline between the Sarmatians and the eastern groups (Fig. 2, A, B, and D) suggest that the Sarmatians descend from a related but different LBA gene pool compared with the one that contributed to the eastern Scythians (likely differently located along an LBA admixture cline). Given the geographic location of the earliest Sarmatian sites found so far, we hypothesize that this gene pool originated in the LBA southern Ural area (Fig. 4B). More data from the later and westernmost Scythian cultures of the Caucasus and eastern Europe will provide a better understanding of their genetic affinities with the earlier Scythians from the Kazakh Steppe analyzed in the current study. Furthermore, our results show that the northern sedentary Sargat-related cultures show a close genetic proximity with the Scythians especially with the eastern nomad groups (Fig. 2B). The Sargats show additional affinity not found in the Scythian groups ultimately related to a northern Siberian lineage (Figs. 2D and 3A). This is consistent with the historical hypothesis that the Sargat people formed as a result of admixture between incoming Scythian groups and an unsampled local or neighboring population that possibly carried this extra Siberian ancestry (3, 18).

From the second half of the first millennium BCE, we detect a major genetic shift in a number of outliers that are interestingly linked with the emergence of the Korgantas culture that replaced the Tasmola in central Kazakhstan. In particular, we observe an influx from an eastern Eurasian source that is different from the one that contributed to the shift in the LBA (Figs. 3A and 4C and table S2). At the turn of the first millennium CE, this mixed genetic profile became widespread among the northeastern individuals associated with the Xianbei-Hun cultures and the later medieval individuals (Figs. 2, C and D, 3B, and 4C, and table S2). The highly variable admixture proportions and dates obtained for those individuals suggest that this was an ongoing process that characterized the first centuries CE (first to fifth century at least; Fig. 3C, fig. S4, and table S3). Additional genetic data from the first millennium CE will allow a more comprehensive understanding of the nature and the extent of this heterogeneity. Instead, in the southern Kazakhstan region, the individuals from the Konyr Tobe site located in the ancient city of Otyrar Oasis show a different genetic turnover mostly characterized by an increase in Iranian-related genetic ancestry, most likely reflecting the influence of the Persian empires (Fig. 4C) (20, 29). Outliers, with high eastern Eurasian admixture or with gene flow from South Asia, suggest that the population of this city at that time was heterogeneous (Fig. 2C and data file S4). During this period, Otyrar was a main center of the Kangju kingdom and a crossroad along the Silk Road (29). In the neighboring region of the Tian Shan mountains, in the third century CE site of Alai Nura, a genetic profile typical of the much earlier IA Tian Shan Sakas can still be found (Fig. 3B and data file S4).

The heterogeneity and geographic structuring observed during the IA, the Xianbei-Hun, and the medieval periods in Kazakhstan come in strong contrast with the genetic homogeneity observed among present-day Kazakhs (fig. S5). Fine-scale haplotype-based analyses confirmed this homogeneity and showed, in line with previous findings (26), that the Kazakh gene pool is a mixture of different western and eastern Eurasian sources (table S4). Our results on the ancient populations revealed that this was a result of the very complex demographic history, with multiple layers of western and eastern Eurasian ancestries mixing through time. The admixture dates obtained for present-day Kazakhs overlap with the period when the Kazakh Khanate was established (~15th century CE; table S5). Furthermore, the gene pool of present-day Kazakhs cannot be fully modeled as a mixture of post-IA northern Xianbei-Hun and southern Kangju-related gene pools (data file S4). These findings suggest that recent events, likely enfolding during the second millennium CE, were associated with more demographic turnovers in this region that ultimately lead to the homogenization of the Kazakh gene pool as a consequence of the establishment of the Kazakh Khanate with its strict exogamic rules (21).

SUPPLEMENTARY MATERIALS

Supplementary material for this article is available at advances.sciencemag.org/cgi/content/full/7/13/eabe4414/DC1

Last Edit: Mar 27, 2021 3:56:16 GMT by Admin

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The Scythians: Who Were They? Jan 14, 2022 20:23:35 GMT

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Ancient genomic time transect from the Central Asian Steppe unravels the history of the Scythians

Abstract
The Scythians were a multitude of horse-warrior nomad cultures dwelling in the Eurasian steppe during the first millennium BCE. Because of the lack of first-hand written records, little is known about the origins and relations among the different cultures. To address these questions, we produced genome-wide data for 111 ancient individuals retrieved from 39 archaeological sites from the first millennia BCE and CE across the Central Asian Steppe. We uncovered major admixture events in the Late Bronze Age forming the genetic substratum for two main Iron Age gene-pools emerging around the Altai and the Urals respectively. Their demise was mirrored by new genetic turnovers, linked to the spread of the eastern nomad empires in the first centuries CE. Compared to the high genetic heterogeneity of the past, the homogenization of the present-day Kazakhs gene pool is notable, likely a result of 400 years of strict exogamous social rules.

INTRODUCTION
The transition to the Iron Age (IA) marks one of the most important events in the history of Eurasia. At the turn of the first millennium BCE, changes in the archeological record attest to the rise of several nomad cultures across the steppe, from the Altai to the western fringe of the Pontic-Caspian region (1). These cultures are often collectively referred to as Scythians based on the common features found in their mortuary contexts (2). Compared to the preceding Bronze Age (BA) populations, the Scythians went through a transition from a sedentary to a nomadic cattle-breeding lifestyle, showed an increase in warfare and advancements in military technologies (e.g., new types of iron weapons and horseback riding techniques, such as introducing the use of a saddle), and the establishment of hierarchical elite-based societies (3).
Previous genomic studies have detected large-scale genetic turnovers (and therefore substantial human migrations) in the BA steppe, which eventually resulted in the formation of a homogeneous and widespread Middle and Late BA (LBA) gene pool that characterized the sedentary herders of the western and central steppe (“steppe_MLBA”) (4–7). The reasons that prompted the rapid decline of these MLBA cultures and the rise of the Scythians are still poorly understood. Scholars have pointed out, among the most relevant factors, the climatic humidification (8) and socioeconomic pressures from the neighboring farming civilizations, i.e., the ones linked to the Bactria Margiana Archaeological Complex (“BMAC”) (3). Three competing hypotheses have been debated regarding the origins of the Scythians: a Pontic-Caspian origin, supported by their assumed Iranian languages, a Kazakh Steppe origin supported by the archaeological findings, and a multiple independent origin from genetically distinct groups that adopted common cultural traits (2). The limited number of genomes so far retrieved from the IA steppe nomads provides a glimpse of their genetic diversity but is far from being sufficient to characterize complex patterns of admixture between various eastern and western Eurasian gene pools (9–12).
From an archaeological perspective, the earliest IA burials associated with nomad-warrior cultures were identified in the eastern fringes of the Kazakh Steppe, in Tuva and the Altai region (ninth century BCE) (13). Following this early evidence, the Tasmola culture in central and north Kazakhstan is among the earliest major IA nomad warrior cultures emerging (eighth to sixth century BCE) (13). These earlier groups were followed by the iconic Saka cultures located in southeastern Kazakhstan and the Tian Shan mountains (sixth to second century BCE), the Pazyryk culture centered in the Altai mountains (fifth to first century BCE-CE), and the Sarmatians that first appeared in the southern Ural region (sixth to second century BCE) and later are found westward as far as the northern Caucasus and eastern Europe (fourth BCE to fourth CE) (1, 14–17). The nomad groups also influenced their sedentary neighbors, such as the ones associated with the Sargat cultural horizon (fifth to first century BCE) located in the northern forest-steppe zone between the Tobol and Irtysh rivers (3, 18).
After the IA, the Kazakh Steppe served as a center for the expansion of multiple empires, such as the Xiongnu and Xianbei chiefdoms from the east (19) and the Persian-related kingdoms from the south (e.g., Kangju) (20). These events brought the demise of the eastern Scythian cultures, but the demographic turnovers associated with this cultural transition remain poorly understood (20). Furthermore, forms of nomadic lifestyle persisted in the Kazakh Steppe throughout the centuries. A key event in the recent history of the nomad populations happened in the 15th to 16th century CE when all the tribes living in the territory of present-day Kazakhstan were organized and grouped into three main hordes (Zhuzs): Elder Zhuz, Middle Zhuz, and Junior Zhuz located in southeast, central/northeast, and west Kazakhstan, respectively (21, 22). This division was a political and religious compromise between different nomadic tribes, which were spread across Central Asia and had to protect themselves from external threats after the collapse of the Golden Horde. This set the basis for the foundation of the Kazakh Khanate (1465 to 1847 CE). Today, Kazakh groups in Kazakhstan still maintain their tribal affiliations and revere their nomadic history preserving some aspects of its culture (21). One of these traditions is the “Zheti-ata,” which consists of keeping track of the family tree up to seven generations by paternal line to avoid marriage between kins (23).
To understand the genetic structure of the different IA nomadic cultures as well as the demographic events associated with their origins and decline, we successfully generated genome-wide data from 111 ancient human individuals retrieved from 39 different archaeological sites across the Kazakh Steppe (Kazakhstan, Kyrgyzstan, and Russia) and one individual retrieved from a Hun elite burial located in present-day Hungary (text S1). Our dataset densely covers a time span ranging from the eighth century BCE to the fourth century CE and also includes three individuals from the medieval period (Fig. 1 and text S1). We also produced new genome-wide data from 96 modern-day Kazakh individuals belonging to several tribes affiliated to the three major Kazakh hordes (Zhuzh) covering the entire territory of present-day Kazakhstan to better understand how recent historical events have shaped the genetic structure of present-day nomads.

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The Scythians: Who Were They? Jan 14, 2022 22:18:59 GMT

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FIG. 1 Geographic location and dates of the newly reported ancient genomes.(A) Map showing the locations of the 39 archaeological sites where the 117 individuals were retrieved and (B) their respective dates in years BCE/CE. The dates reported are 14C-calibrated (2-sigma) ranges for the sites comprehending at least one individual directly radiocarbon-dated; if more individuals are dated, we report the lowest and the highest values across all of them. If for a site, no individuals are dated, we report the date ranges based on the archaeological context (data file S1). The sites are colored according to their cultural affiliation. This same culture-based color code (top right) is maintained for all the figures in the main text and the Supplementary Materials.

RESULTS
Genome-wide data for 117 ancient individuals were obtained using an in-solution DNA capture technique designed to enrich for 1,233,013 single-nucleotide polymorphisms (SNPs) commonly referred as 1240K capture (Materials and Methods). Genome-wide data for 96 present-day Kazakh individuals were generated with the Affymetrix Axiom Genome-wide HumanOrigins SNP-chip (“HO”) (Materials and Methods). After performing quality controls, we retained all the 96 modern Kazakh individuals and 111 ancient individuals with at least >20,000 SNPs covered, obtaining a median of 793,636 successfully recovered SNPs and 1.5× autosomal coverage on the 1240K panel across all individuals (Materials and Methods and data file S1).

We then merged the new data with a reference dataset of previously published modern and ancient individuals compiling a “1240KHO” dataset consisting of 586,594 SNPs overlapping with the modern genotype data that we used for performing global population structure analyses [i.e., PCA (principal components analysis) and ADMIXTURE]. We also produced a “1240K”-only dataset consisting of 1240K capture or whole-genome shotgun data pooled down to include 1240K sites only that we used for the rest of the analyses (Materials and Methods and tables S2 and S3). For population-based analyses, we grouped individuals according to their archaeological culture affiliation, spanning a defined time range after excluding genetic outliers shifted more than ±2 SD from the median PCs of their respective group (Materials and Methods and table S1).

The IA transition in the Kazakh Steppe
Overall, PCA and ADMIXTURE suggest that a substantial demographic shift occurred during the transition from the BA to the IA in the Kazakh Steppe (Fig. 2 and figs. S1 and S2). In contrast to the highly homogeneous steppe_MLBA cluster found across the Kazakh Steppe until the end of the second millennium BCE, the IA individuals are scattered across the PC space, most notably along PC1 and PC3. Their spread along these PCs suggests a varying degree of extra eastern Eurasian affinity compared to the MLBA population and extra affinity to southern populations ultimately related to the Neolithic Iranians and the Mesolithic Caucasus hunter-gatherers (from here on referred to as Iranian-related ancestry), respectively. Despite the high genetic variability, it is possible to appreciate homogeneous clusters of ancient individuals belonging to the same archaeological culture and/or geographic area (Fig. 2 and fig. S1). Following a chronological order, most of the individuals from the sites associated with the Early IA Tasmola culture (“Tasmola_650BCE”) and the published “Saka_Kazakhstan_600BCE” of central-north Kazakhstan cluster together in the middle of the PCA plot and show a uniform pattern of genetic components in ADMIXTURE analyses (Fig. 2, A and D, and figs. S1 and S2). The two previously published individuals from the Aldy Bel site in Tuva (Aldy_Bel_700BCE) also fall within this genetic cloud (Fig. 2A). This genetic profile persists in the later Middle and Late IA, shown by most individuals from the Pazyryk site of Berel (“Pazyryk_Berel_50BCE”) (Fig. 2B). This IA cluster is distinct from the previous steppe_MLBA groups inhabiting the same regions, most notably because of its substantial shift toward eastern Eurasians along PC1. In addition, we find outliers showing an even stronger shift to eastern Eurasians than the main cluster: two outliers from Pazyryk Berel time (“Pazyryk_Berel_50BCE_o”), three outliers from the Tasmola site of Birlik (“Tasmola_Birlik_640BCE”), and three of four individuals from the Korgantas phase of central-north Kazakhstan (24) (Fig. 2B and table S2). One female individual from Birlik (BIR013.A0101) with an eastern Eurasian genetic profile was unearthed with grave goods (a bronze mirror) that presented typical Eastern Steppe features (text S1).

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The Scythians: Who Were They? Jan 14, 2022 23:44:23 GMT

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FIG. 2 PCA and ADMIXTURE analyses.(A to C) PC1 versus PC3 (outer plot) and PC1 versus PC2 (inner plot in the bottom right box) including all the IA, new and previously published individuals (filled symbols), relevant published temporally preceding groups (empty symbols), and present-day Kazakh individuals (small black points). The gray labels in this and the following panel indicate broad geographical groupings of the modern individuals used to calculate PCA that in the plots are shown as small gray points. The ancient samples are distributed in (A) to (C) sliced in three different time intervals as reported in the top right corner. (D) Histograms of ADMIXTURE analysis (K = 12; fig. S2) for the new IA and post-IA individuals and selected subset of temporally preceding groups maximizing key genetic components and a randomly selected subset of present-day Kazakh from the three main Zhuzs.

The classical IA Sakas from the Tian Shan region to the south (“Saka_TianShan_600BCE,” “Saka_TianShan_400BCE,” and previously published “Pub_Saka_TianShan_200BCE”) are distributed along a cline between the Tasmola/Pazyryk cluster and the Iranian-related gene pool, along PC3 (Fig. 2, A and B). A stronger affinity to the Neolithic Iranians is also found in ADMIXTURE analyses (Fig. 2D and fig. S2). The shift toward the Iranian-related gene pool is found as early as ~650 BCE in one Eleke_Sazy_650BCE individual (ESZ002) retrieved from an elite Saka burial, while three of four individuals from one of the earliest Tian Shan Saka site of Caspan_700BCE fall within the Tasmola/Pazyryk cloud.

The individuals associated with the sedentary Sargat culture in the forest-steppe zone north of the Kazakh Steppe (“Sargat_300BCE”) partially overlap with the Tasmola/Pazyryk cluster although forming a cloud in PCA that is shifted toward western Eurasians and toward the uppermost cline of northern Inner Eurasians (PC1 and PC2, respectively; Fig. 2B). In line with PCA, Sargat individuals carry a small proportion of a different type of northeast Asian ancestry not detected in the nomad groups further to the south (Fig. 2D).
With the exception of one outlier falling in the Tasmola/Pazyryk cloud, the individuals associated with the Sarmatian culture are highly homogeneous despite being spread over a wide geographic area and time period (i.e., early “Sarmatians_450BCE,” late “Sarmatians_150BCE,” and western “Sarmatians_CaspianSteppe_350BCE”; Fig. 2, A and B). Our new data from seven early Sarmatian sites in central and western Kazakhstan (Sarmatians_450BCE) document that this gene pool was already widespread in this region during the early phases of the Sarmatian culture. Furthermore, Sarmatians show a sharp discontinuity from the other IA groups by forming a cluster shifted toward west Eurasians (Fig. 2 and table S2).

Admixture modeling of IA steppe populations
Genetic ancestry modeling of the IA groups performed with qpWave and qpAdm confirmed that the steppe_MLBA groups adequately approximate the western Eurasian ancestry source in IA Scythians while the preceding steppe_EBA (e.g., Yamnaya and Afanasievo) do not (data file S4). As an eastern Eurasian proxy, we chose LBA herders from Khovsgol in northern Mongolia based on their geographic and temporal proximity. Other eastern proxies fail the model because of a lack or an excess of affinity toward the Ancient North Eurasian (ANE) lineage (25). However, this two-way admixture model of Khovsgol + steppe_MLBA does not fully explain the genetic compositions of the Scythian gene pools (data file S4). We find that the missing piece matches well with a small contribution from a source related to ancient populations living in the southern regions of the Caucasus/Iran or Turan [we use the term “Turan” for consistency with (7), only its geographical meaning, designating the southern part of Central Asia; Fig. 3A]. The proportions of this ancestry increase through time and space: a negligible amount in the most northeastern Aldy_Bel_700BCE group, ~6% in the early Tasmola_650BCE, ~12% in Pazyryk_Berel_50BCE, ~10% in Sargat_300BCE, ~13% in Saka_TianShan_600BCE, and ~20% in Saka_TianShan_400BCE (Fig. 3A), in line with f4-statistics (table S2). Sarmatians also require 15 to 20% Iranian ancestry while carrying substantially less Khovsgol and more steppe_MLBA-related ancestry than the eastern Scythian groups.

Last Edit: Jan 14, 2022 23:44:55 GMT by Admin